Hi, welcome to the Magix forums.

First, please read this post and give us all the information requested there, especially since you chose Video Pro X as your product but then asked about MEP.

Can you post a screenshot of the error message that you see?

You say I uploaded a file for me to start editing then I needed to activate it but you cannot use MEP for any purpose, in my experience, until after you have completed the activation so I am not sure how you could have opened a file in the program before you activate it.

Please give us also step by step exactly what you did. With this greater level of information we might be able to help you.

Jeff